Measuring and controlling instrument



April l2 1927. l 41,624,887 E. H. BRISTOL MEASURING AND CONTROLLING INSTRUMENT Filed Aug. 1o, 1920 5 Sheets-Sheet l April 12, 1927.

E. H. BRISTOL MEASURING AND CONTROLLING INSTRUMENT Filed Aug. l0, 1920 I5 Sheetssheet 2 Ih/vena? anHBulsoZ. M M f April 12 ,1927.

E. H. BRISTOL MEASURING AND GONTROLLING INSTRUMENT Filed Aug. 1o. 1920 3 Sheets-Sheet 5 Patented Apr. 12, 1927.

UNITED STATES 'PATENT OFFICE.

EDGAR H. BRISTOL, F FOiXBORO, MASSACHUSETTS, ASSIGNOR TO THE FOXBORO COM- `EANY, OF FOXBORO, MASSACHUSETTS,

A CORPQRATION OF MASSACHUSETTS.

, -MEASURING AND CONTROLLTNG INSTRUMENT.

Application led August 10, 1920. `Serial No. 402,665.

This invention relatesto automatic conexist at a certain point and as they may be modified. Herein I have shown an instru-` ment which controls the passage of fluid through a conduit', which fluidy may'either directly effect the conditions being measured or control the same through lintermediate mechanisms. For definiteness I have chosen yby Way of example of my invention an instrument adapted to measure temperature conditions and 1n partlcul'ar one easuring temperature by a sultable pressure sensitive Adevice and recording the measurements on al suitable dial.

An instrument performing these functions alone is commonly known as a recordingI thermometer or therniograph.4 The present device is also a controllingI in# strument and controls the assa e'of4 fluidl through a conduit, the fluiI in t e example chosen being under 'positive pressure.

My' invention will be best understood 'by reference to the following detailed description of the embodiment thereof referred to which is illustrated in the accompanying drawings, wherein:

Fig. lisa frontelevation of the instrument;

Fig. 2` is a similar View of the same with the door and the frontface removed to show the interior;

`Fig. 3 is an enlarged perspective View oft certain portions of the operating mechani'sm';

F ig. 4 is a partly broken view on an enlarged scale showing the electrical arrangement of parts of the operatingimechanism;

Fig. .5 is an elevation yof a cont-act maker and'cooperating contacts forming part of thc mechanism,-

Fig. G is a section on line 6 6 of Fig. 5;

Fig. 7 is a view in vertical section of a fitting of the pressure conduit and some of the controlling mechanism therefor;

Fig. 8 is a view on a still larger scale and with parts broken away of details of Fig. I; and

Fig. 9 is a section on the line 9-c9fof Fig. 2 on an enlarged scale.

as a vulcanizer.

Referringto Figs. 1 and 2, the instrument shownembodies a suitable case 9, Fig. 2, the front of which may be `covered by a glazxed door 11, Fig. 1, through which is displayed the dial of the instrument,- here shown as the usual removable polar chart 13 adapted to be rotated by the shaft 15 of a suitable time train, not herein shown in detail but ofwhich the enclosing casing 17 appears in Fi 2. The 'measuring element herein takesjt e form of a pressure 'sensitive device although other forms of res onsive elements can be used. Herein I ave shown a flat helical tube 19 (see Figs. 2 and 3) supported at one endl and secured at its other end to a shaft 21 which is adapted to move, in the present instance by connections hereinafter to be'described, the index or pen 23 which sweeps over the chart 13 marking the same in well known manner.

The tube may be connected by 'a capillary pipe 25 conveniently protected by an armor 27 at the exterior ofthe casing with a bulb 29 adapted. to lie exposed to temperature conditions atthe point whichvit is desired to measure them. It will be understood that the bulb 29, pipe 25 and tube 19 may be lledwith fluid such as alcohol andl that the changes ofvapor tension caused by changes of temperature will vdistort the tube 19 and actuate the pen 23. As best'shown in Fi 3, the pen 23 may be mounted'on a sha t 31 carrying a crank arm 33 connected by a connecting rod 35 to the parallel crank arm 37 on the shaft 2l moved by the sensitive tube 19.

The' instrument here shown is adapted to control the passage of fluid under pressure from the pipe 39 to the pipe 41. In other words, in the embodiment of the invention illustrated, the flow of fluid xwhich is to be controlled is from right to left viewing the drawings. It will be understoodl that the fluid flow may be utilized to control other mechanisms. For example, air under pressure may passthrough thel pipes 39 and 41 and operate a diaphragm motor valve. ofv

known type controlling the passage of steam or other heating medium to a chamber such Herein communication is provided between pipes 39 and 41 by a fitting 43y secured to and extending into the instrument case. As best seen in Fig. 7,

. the fittingA 43 provides a connection between casing 9, andthis port is adapted to be sealed by a valve 53 carried by the tubular valve rod 55. Also carried by this valve rod is a valve 57 adapted, when the valve 53 is withdrawn to the right away from its seat, to seat on a valve seaty 59 herein shown as nformed in dthe end of a sleeve 61 carried by a screw plug 63 and fitting the connecting passage This sleeve also forms a guide for the valve carrying Vrod as best seen in Fig. 8, the rod, however.r tting loosely therein to permit the passage of pressure fluid around the same from passage 47 through the opening or port 65 inthe side of sleeve 61.

The hollow valve rod 55 is carried by and communicates with an expansible diaphragm 67 herein shown as supported by a bracket 69 extending from fitting 43. The parts are so designed that when the diaphragm 67 is in its normal condition it is under mechanical tension, the v alve 53 is lheld seated and communication is open between pipes 39 and 41. As pressure fluid flows through the fitting 43, a certain amount 'will enterthe hollow valve rod 55 at the right hand end,

viewing Figs. 7 ,and 8. and is permitted to escape or bleed therethrough, through the diaphragm 67 and (see Figs. 2 and 3) through flexible connecting tube 71 and through an exhaust port 73 in a terminal member 75 to the atmosphere within the interiorrof casing 9. It will be understood that the passage through the valve rod 55 is so minute that the escape of pressure fluid does not materially affect the flow.

When it is desired to interrupt the flow of pressure fluidthrough the pipes 39 ,and 41, the exhaust port 73 may be-closed by means hereinafter to be described. Pressure fluid entering through the valve carrying rod 55 cannot escape at 73 and w'ill expand diaphragm 67, thus cutting ofi'7 the passage 45 from the passage 47, interrupting the flow of pressure fluid to pipe 41 and relieving the existing pressure in the latter through port 51. vThe mechanism just described is substantiallyI similar to that shown and described in my Patent No. 1,326,640, dated Dec..30,J 1919.

I shall next describe the means herein uti- 'lized for controlling the motor diaphragm 67` andhence the valves 53 and- 57; In the present embodiment of the inventionthe measuring tube 19 which measures the temperature is also used'a's a controllingdevice and provides for interrupting-thei-flow of pressure fluid through pipes 39 and 41 when the temperature surrounding bulb 29 is at `a certain point. Referring to Figs. 3 and 4. the port 73 and the member 75 may be closed by a valve conveniently in the form of a strip 79 loosely pivoted coa'xially with' iiig the crank arm 37 counter-clockwise the crank ar1n33 will move valve 79 away from the port in the cooperating valve memberl 75' and this will allow the flow of fluid to pipe 41. Through any suitable mechanism not here necessary to describe this effect may cause the operation of lsuitable means for causing heating to take place at the point tofbe measured. As the temperature rises again the crank arm 33 will move clockwisepermitting the valve 79 to be lowered against the valve element 75 to close the port and eventually to cut ofi' the supply of heat. It will be noted that if the heat rises further beyond this point the crank arm 33 can move on as it has lost motion relative to the valve 79. l

Mln the embodiment of the invention here shown I provide for an automatic control of the heat providing Jfor different values thereof at-difi'ercnt times. It will be understood from the description already given that if the valve element 75 occupies a given position, that 'position will corrcspoiulto a desired temperature at a chosen point which will be maintained substantially constant by the control of the heating instrumentalities through the. instrument. If the position of one of the valve elements, for example thel valverlement 75, is shifted there 'is a corresponding change in value of the temperature .at which the control mechanism takes effect. Herein I provide for more or less relative shift-ing of the elements of the valve couple throughout ay time period so that the control-of the instrument is a function otl two variables, one temperature or pressure shaft 31 and\ the. bearing for the valve 79. Positioning of the valve element lnay be aped arm 83 pivoted by its other leg on shaft 85 coaxial, with the' effected by a suitableA cam/87 on the time 13' shaft 15 which swingsa lever 89 pivoted at 91 agamst the Lforce of a'spring`-93 .and which through a connecting link 95 swings I the arm 83about its axis.

As the arm 89 rides on the rise of the cani the valve element 75 1s swung away fromu thc'coope/rating valve 70 which is held by 4the crank arm --ll operated by the sensitive tube 10. Airexhausts through port 73 and heatis applied tothe desired point. As the4 temperature rises to the point determined by the position ot the valve elen'ient 75, the lvalve 79 is permitted to swing over der 97 against which lits a hub member 0f) having a :Bange 101.A The cam r37 may bc loosely received over the liubfnieniber and clamped against the flange 101 by the nut 103. A dial holder or chait carrier 105 whichmaylieland preferably Vis of the type described in' Patent No. 1,04S,8ill dated Dec. 31., 1912. is secured vto, the shaft '15 and received within the threaded surface ole hub 99 serves as an axle nut for clamping the same. screw100 locks the chart cai'- rier 105." A suitable spring washer 1071s` preferably interposed `between the chart carrier and the hub to cause/the hub to rotate with the time shaft. .The nut'103 surrounds the chart holder 105 and may be withdrawn over the sanic without disturbs ing it. This construction permits the cams to he readily changed and conveniently positioned as regards the time train and toi.:

easy relativeadjustment ot'nlthe cam and they chart. j

In the present form ot' the invention means are provided to assure the accurate functionini,r of the instrument. Conveniently this takes the form of a mechanism electrically controlled nand-operated at times when the instrument is'not functioning with desired accuracy. By way of example I 'here disclose an alarm to attract attention to the` fact. lt will be understood that in the operation of a device of this character one valve ele-l e ment as 79 .follows the ,other` element 75 very closely` in its movement. the normal position of the parts belnga slight separa- Y tion. I-f the temperaturedoes not rise accordiner to the desired curve the Avalve element 79 will lag4 undulyfarfb'ehind. y Means may therefore be provided to give a Isignal dn vundue separation of these elements. On

the other hand, if the temperature rises unduly Athe crank 'arm 33' b virtue ofy its lost motion connection with the. valve 79 will swing,r clockwise away from the saine. and a signal should therefore be given in this instance.` In the present instance means are provided controlled by the position-of the arm 33, that is to say, by the position of the i tube 19 and ultimately by the temperature which 1s being measured, for closing an electric circuit when the position rof this arm varies unduly relative lto the ypositionv ot the valve element 75, in other words, whenthe temperature beingi measured varies unduly from the Set temperature for. the -griventime Referringi to Fig. 3, there is ,there shown "a contact maker in the form of a light arm 111 pivoted at 11.2 to the base or connecting` portion ofthe Ushaped arm y 83 and normally swung by a light spring 113 against a shoulder 115 at' the extremity of a wire '117 VIAcarriedby the crank arm 33,

this wire extendingr from the shoulderin a.

loner curved portion 110 for a purpose hereinafter to be described (see Figs. 5 and 6).j

A lso ,carriel by the arm 83 as shown in Fig. 5 and movable therewith by the time train are arc-shaped contacts 121 and 123, which maybe formed on the 'end ol arms pivoted to the base flange of the arm 83 andadjustable screws A125 to. bring.y them nearer or further away froiirthe normal medial position of the contact .maken 111` which is in parallelism with the shaft 85. During normal operation of the instrument `when the valve 79 is in contact with the arm 33 and either in contact with the cooperating valve element 75 or but slightly distant ytherefrom` the contact` maker 11.1 'which is'positioned by the arm 33 lies are-positioned by the arm carrying .the valve 75, the distance between these con- `tacts providinga certain freedom of movement for the contact maker 111 correspondingr to the desired permissible range of movement between the elements ot the valve couple 75 and 79. It the temperature lags,

however, andv the valve element with the contacts moves clockwise viewin,f r Figs. 3 and 5 without Acorespondinir movement of the arm 33, the contact maker will he held back bv the shoulder 115 of the wire attached to this arm, the fulcruin 112. however` moving 4on with the arm 83 an'l the contact maker will be swung into contact with the arcshaped contact 121, thus closingY an electric circuit andeithersounding an-alarin,or operating suitably relay mechanism t'or correcting' the undue conditions. On the other hand, if the temperature rises too fast the fulcrum ot thecontact maker will remain 'stationary'. relativeli7 speaking, and the arm 33 will move clockwise releasinq the Contact maker to the action-ofthe spring 113 and it between the two arc-shaped contacts which iw i i llt) will swing over on to the arc-shaped Contact 123 with similar results. In the former'instance as the temperature falls the curved extension 119 of the wire will ride under the shoulder 127 on the contact maker and sustain the same and prevent it from falling over on the opposite side of the wire. Referring to Figs. 2 and 4, the contact *.arin 111 which has a suitable brush 129 supported on a bowed wire 131 may be grounded to the case ot the instrument which is provided with a ground terminal 1233. arc-shaped contacts 121 and 123 on the other handv are insulated as indicated by Fig. 4 and connected by wire 135 to the insulated terminal 137. To these terminals are connected the wires of the cii'ciiit ot' tlie 'alarm bell 139. Fig. 2. or otliei' electrically opei'- -ated or controlled mechanism..

In Fig. 2l there is shown a pointer 1-ll carried by the shaft on which is mounted the arm S which carries the contacts and the valve element 75. rlliis pointer extends over the chart 13 as shown in Fig. l and givesa visual indication of the position of the valve element 75 in comparison with the indication afforded by the pen 23 which shows the position of the valve element 79 as positioned byy crank larm 323 on the shaft 31 which carries the pen 9.3. In Figs. 1,`

' and 3 for clearness the ipointer 141 is shown -would be thev case in practice since. as

much further lremoved rom the pen Q3 than has been explained. the valve elements 75 and 79 are in the normal operation of the instriiment very closeto one another.

The path of the pointer 141 on the chart is a curve indicating the controlling action ot the instrument. To cause this curve to follow or coincide with the temperature curve an adjustment is preferably provided to alter the positions of the valve element 75 between which it. is moved by the cani ST. Referring to Fig. 2, this is provided for in the present embodiment of the invention b v an adjustment of the pivotal point 9i' of lever 89.

Herein the pivot 91 is disposed eccent-iically on a swinging lever 143 pivoted to tit) a pillar 145. By swinging lever 143 the position of pivot` 91 is adjusted and consequently the position of the valve element 7 lVithin the limits of the adjustment, therefore, the position of the valve element corresponding to a certain point on the cam may be adjusted to correspond with a desired temperature. The lever 143 may have a rebent end 147 adapted to project through a, slot- 149 in the :tace of the instrument as shown in Fig. l, this end forming a pointer adapted to cooperate with a suitable scale as shown.

I have described in detail the particular embodiment ot' my invention shown by way of example in the accompanying drawings. The principles exemplilied thereby which I claim as new and desire to secure bv Letters latent I shall express in the ollowing claims 1. An instrument of the class described havingr means for controlling the -tiow of fiuid as a function of both time and temperature variables and including a thermosensitive device and an electric mechanism hav-c by atleast a 4predetermined amount' from the desired value corresponding to a given time value.

3. An instrument of the class described comprising controlling means including a pair of `valve, elenients, means for moving one in accordance.with a pressure variable, means for relatively positioning the two in -accordance with another variable and signal means operated on predetermined separation of said elements.

4. An instrumentotthe class described comprising controlling means including a pair of valve elements, means for moving one in accordance with a pressure variable, means for relatively positioning the two in accordance with :mother variable, electric contacts moved in accordance with said variables and normally separated at such rallies thereof which maintain the valve elements in close proximity. y

5. An instrument of the class described `comprising controlling means including a variably positionable valve element, a cooperating valveJ element, pressure responsive means operatively related thereto to control movement of the same and signal means operated on predetermined separation of said elements.

` 6.V An instrument of the class described comprisingr controlling means including a variably positionable valve clement, a cooperating valve element, pressure responsive means operatively related vthereto to control movement lof the sameiand providing Ji'or closing of the valve at a given pressure valuel for a given position ot the ,firstelement and signal means operated when said pressure responsive means responds lto a predeterymined different value.

7. An instrument of the class described co'mprfsing controlling means including a valve element, means for positioning the same, an electric Contact adjacent thereto llt) ylo

"and moved therewith, a cooperating valve shiftable valve, element, electrical contacts on either side thereof, a swinging contact .arm between them, a cooperative valve element and temperature responsive means controlling movement of said cooperating element and also of said arm. f

10. An instrument of the class ,described comprisinga valve element, electricalcontacts adjustably positioned adjacent -said element on either side thereof, a swinging contact arm pivoted to -lier bet-Ween said con-v tacts, means for moving said element, contacts and arm as a unit, a cooperating valve`r` element and temperature responsive means controlling movement of said latter element andfofsaid arm.

11 An instrument of the class described comprising controlling means including a valve element,.an electrical contact definitely positioned with' respect thereto, a movable contactarm to cooperate with said contact, said element, contact and arm variably positionable as a unit, a cooperating valve element and pressure responsive means controlling movement of said latter element and of 5 saidA arm. J

` 1n. ,valve element, a cooperating valveeleme 12. An instrument as defined in claim 11 wherein time controlled means serve for variably positioning the element, contact and arm.

13. In a structure iof the class described, in combination with the swinging contact maker 111 having a transverse shoulder, means for moving the same having a shoulder engagin one side of the arm and a long",Y extension a jacent said latter shoulder to underride vthe transverse shoulder` and/ support the arm after movement of the same.

14. In an instrument of the class described a valve element, a cooperating valveelement comprising a pivoted s ring pressed arm normally pressed towar the first, a' swinging arm'member engaging one sidek of said first arm, a pressure responsive element and n. connecting rod between said element and.' said secondarm. 4 c c 15. In an instrument of the class describef sev U comprising a pivoted spring pressed arm normally pressed toward the first, a swin ing arm member engaging one side of sald iirst arm and a pressure responsive device in the form of a helical tube connected to said second arm to swing thesame.

16. An instrument of the class described comprising controlling means including a valve element, a swinging arnr sup orting the same, a cam' having time-train driving means for moving the arm, a cooperating Valve 'element arranged to swing about the same axis as the arm,'a spring to move the same in one direction, a crank arm rotatable on said axis having a portion engaging said element to vmove the same in the other direction and a pressure responsive device foractuating said crank arm.

. 17. An instrument of the class described comprising controlling Wmeans lincluding -a valve element, a pivoted arm spring pressed, toward the same and providing a cooperating valve element, parallel cranks and a connecting :rod between them,- pressure responsive lmeans for moving one crank, the other crank being `positioned to make contact with a side of said arm.

comprising controlling means including a valveelement, a swinging arm sup orting the same, a cam having time-train riving means for moving the arm, a cooperating valve element arranged to-swing'abo'ut the same axis as the arm and a pressure responsive device operatively connected to the latter valve element.

19. An instrumenty of *the class described comprising controlling means includingl a valve element, a' swinging .arm supporting the same, a camhaving time-train driving means, an arm oscillated thereby and connected to said first arm, a cooperatingvalve element,y arranged to swing about the same ,axis as theiirst arm and a pressure responsive device operatively connected to the latter valve element.

20. A combined recording and controlling instrument comprising a clock movement having a shaft, a dial plate rotatable thereby, a pen, a pressure responsive member moving 'the same, governing mechanism including a valve element operated by said member, a cooperatin valve element and a cam on the time sha t nfor positioning said latter element.

21. bIn a combined recording and controlling instrument as described, atime shaft, a h'ub thereon, a, dial holder serving as an azi-le nut for said hub, a cam fitting over said hub anda nut forclamping the cam `to the hub.

22. In a combined recording and controlling instrument as described, a time shaft, l. hub thereon, a. dial holder serving as an axle 'm nut for said hilb, aspring washer between 18. An instrument of the class described lIl() said holder and hub, a cam fitting over said 'hub and a nut for clamping the cam to the hub.

23. A combined recording and controlling instrument comprising a clock movement having a shaft, a dial plate rotatable thereby, a pressure responsive member ad jacent the circumference of the dial, a pen moved by said member to sweep outwardly from the center of the dial, governing mechanism including a valve element operated by said member, a cam on the time shaft, a motion transmitting device movable by said cam and a second cooperating valve element positioned by said device.

24. A combined recording and controlling instrument comprising a clock movement having a shaft, a dial plate rotatable thereby, a pressure responsive member adjacent the circumference of the dial, a pen moved by said member to sweep outwardly from the center of the dial, governing mechanism including a valve element operated by said member, a'cam on the time shaft, a motion transmitting device movable by said cam, a second cooperating valve element adjacent said pressure responsive member, a hand movable therewith pivoted substantially coaxially of the pen and cooperating with the dial to indicate the position of' said second valve element, said second valve element being positioned by said device.

25. An instrument of the class described comprising controlling means including a pair of valve elements, a pressure sensitive device for moving one of the elements and means for relatively positioning the elements including a cam and a lever moved thereby having an adjustable lp ivot.

26. An instrument of the class described comprising controlling means including a pair of valve elements, a pressure sensitive device for moving one of thev elements and means for relatively positioning the elements including a cam, a lever moved thereby and a swingable support on which the lever is eccentrically pivoter` 27. An instrument of the class'described comprising controlling means including -a pair ofvalve elements, a pressure sensitive device for movin one of the elements and means for relative y positioning the elements includingA a cam and motion transmitting means operated by the cam adjustable to alter the positions of the element which is moved thereby.

28. A combined recording and controlling instrument comprising a clock movement having a shaft, a dial plate rotatable thereby, a pressure responsive member adjacent the circumference of the dial, a pen moved by said member to sweep outwardly from the A `center of the dial, governing mechanism including an element`operated by said member, a cam on the time shaft, a motion transmitting device movable by said cam' and a second element cooperating with the 4first and positioned by said device. A

29. An instrument of the class described comprising controlling means including a variably positionablecontrolelement, a cooperating control element adapted to be brought into contact therewithto effect theV desired action, pressure responsive means operatively related to said second element to Vcontrol movement of the same and providing for the contact of said elements at a given pressure value lfor a given position ofthe first element and signal means operated when said pressure responsive means responds to a predetermined different value.

30. An instrument of the class described comprising controlling means including a shiftable control element, electrical contacts Aon either side thereof, a contact maker movpivoted adjacent said contact, means for L moving said element, contact and contact maker as a unit, a second control element adapted to engage the first to effect the desired action and pressure responsive means controlling movement of said latter element and of said contact maker.

32.v An instrument of the class described comprising controlling means including a pair of control elements adapted one to engage the other to effect the desired action, a pressure sensitive device for moving one of the elements and means for relatively positioning the elements including cam and mgtion transmitting means operated by the cam adjustable to alter the positions of the element which is moved thereby.

33. An instrument of the class described comprising controlling means including a swingable arm carrying a valve element, a. second arm pivoted -on the same axis, alcooperating valve element arranged to be moved in one direction by said arm but having lost motion relative thereto in the other direction, a -pressure sensitive device for moving the second arm, the whole constituting a device wherein adjustment of the control may be effected by an angular movement of the first arm equal to' the known angular movement effected by the pressure sensitive device under a given variation in pressure.

34. An instrument of the classv described comprising controlling means including a swingable arm carrying a valve element, a cooperative valve element pivoted on the .l'sive device for moving the second arm, the

Whole\'constituting` a device wherein adjust-l ment'of the control may be effected by an angular movementof the first arm equal to the known angular movement effected by the l pressure -sensitive device under a given Varlation in pressure.

'35. A combined controlling instrument and gage comp ising a pressure -sensitivefelelment; an index moved thereby, a scale with which the index cooperates,a mechanism comprising a first control element and a second control element normally spring pressed toward the first andadapted to cooperate vtherewith to effect the desired action and -lneans connecting said pressure sensitive element to said second control element to move itin one direction against the spring and having lost motion with respect thereto in t-hetother direction. l y

36. A combined controlling instrument and gage comprising a pressure sensitive element,an index moved therebyf, a scale With which the index cooperates, al mechanisnr comprising afirst control element and av second 'control element and means conindgpendnt of the former after the controll an elements are engaged,

B7. A combined controlling" instrument and gage comprismg a pressure sensitive element, an index moved thereby, a scale with which the index cooperates, a controlling valve comprising a first valve element and a second, valve element normally tending to seat relatively to the first and means connecting said secondelement to said pressure sensitive device to be moved thereby permitting continued movement of the latter independent ofthe former after the seating.

38.v A Itime and pressure control instrument comprising a pressure responsivedev vice, avmechanism including control ele- Inen s adapted to engage one With'the other to efl'ect the desired action and a clock movement, an enclosing casing for said parts including a front plate through which the time shaft on the clock movement projects,

means' for posltloning one` of said control ycenter defined by saidxshaft visually 1nani.

testing the position of -said element under control of the cam whereby the controlling pressure may be read in the manner familiar in the reading of recording instruments;

In testimony whereof, I have signed my name to this specification.

EDGAR H.. BRISTOL. 

